Back in April, there was a huge fuss over an internal report by the Department of Homeland Security warning that current conditions resemble those in the early 1990s â€” a time marked by an upsurge of right-wing extremism that culminated in the Oklahoma City bombing.

Conservatives were outraged. The chairman of the Republican National Committee denounced the report as an attempt to â€œsegment out conservatives in this country who have a different philosophy or view from this administrationâ€ and label them as terrorists.

But with the murder of Dr. George Tiller by an anti-abortion fanatic, closely followed by a shooting by a white supremacist at the United States Holocaust Memorial Museum, the analysis looks prescient.

There is, however, one important thing that the D.H.S. report didnâ€™t say: Today, as in the early years of the Clinton administration but to an even greater extent, right-wing extremism is being systematically fed by the conservative media and political establishment.

Now, for the most part, the likes of Fox News and the R.N.C. havenâ€™t directly incited violence, despite Bill Oâ€™Reillyâ€™s declarations that â€œsomeâ€ called Dr. Tiller â€œTiller the Baby Killer,â€ that he had â€œblood on his hands,â€ and that he was a â€œguy operating a death mill.â€ But they have gone out of their way to provide a platform for conspiracy theories and apocalyptic rhetoric, just as they did the last time a Democrat held the White House.

And at this point, whatever dividing line there was between mainstream conservatism and the black-helicopter crowd seems to have been virtually erased.

Exhibit A for the mainstreaming of right-wing extremism is Fox Newsâ€™s new star, Glenn Beck. Here we have a network where, like it or not, millions of Americans get their news â€” and it gives daily airtime to a commentator who, among other things, warned viewers that the Federal Emergency Management Agency might be building concentration camps as part of the Obama administrationâ€™s â€œtotalitarianâ€ agenda (although he eventually conceded that nothing of the kind was happening).

But letâ€™s not neglect the print news media. In the Bush years, The Washington Times became an important media player because it was widely regarded as the Bush administrationâ€™s house organ. Earlier this week, the newspaper saw fit to run an opinion piece declaring that President Obama â€œnot only identifies with Muslims, but actually may still be one himself,â€ and that in any case he has â€œaligned himselfâ€ with the radical Muslim Brotherhood.

And then thereâ€™s Rush Limbaugh. His rants today arenâ€™t very different from his rants in 1993. But he occupies a different position in the scheme of things. Remember, during the Bush years Mr. Limbaugh became very much a political insider. Indeed, according to a recent Gallup survey, 10 percent of Republicans now consider him the â€œmain person who speaks for the Republican Party today,â€ putting him in a three-way tie with Dick Cheney and Newt Gingrich. So when Mr. Limbaugh peddles conspiracy theories â€” suggesting, for example, that fears over swine flu were being hyped â€œto get people to respond to government ordersâ€ â€” thatâ€™s a case of the conservative media establishment joining hands with the lunatic fringe.

It s not surprising, then, that politicians are doing the same thing. The R.N.C. says that â€œthe Democratic Party is dedicated to restructuring American society along socialist ideals.â€ And when Jon Voight, the actor, told the audience at a Republican fund-raiser this week that the president is a â€œfalse prophetâ€ and that â€œwe and we alone are the right frame of mind to free this nation from this Obama oppression,â€ Mitch McConnell, the Senate minority leader, thanked him, saying that he â€œreally enjoyedâ€ the remarks.

Credit where credit is due. Some figures in the conservative media have refused to go along with the big hate â€” people like Foxâ€™s Shepard Smith and Catherine Herridge, who debunked the attacks on that Homeland Security report two months ago. But this doesnâ€™t change the broad picture, which is that supposedly respectable news organizations and political figures are giving aid and comfort to dangerous extremism.

What will the consequences be? Nobody knows, of course, although the analysts at Homeland Security fretted that things may turn out even worse than in the 1990s â€” that thanks, in part, to the election of an African-American president, â€œthe threat posed by lone wolves and small terrorist cells is more pronounced than in past years.â€

And thatâ€™s a threat to take seriously. Yes, the worst terrorist attack in our history was perpetrated by a foreign conspiracy. But the second worst, the Oklahoma City bombing, was perpetrated by an all-American lunatic. Politicians and media organizations wind up such people at their, and our, peril.